Flexible potentiometer

ABSTRACT

A deflectable substrate such as a phenolic resin has a conductive ink deposited thereon in a pattern preferably with a segmented conductor position on top to form a flexible potentiometer in which the resistance consistently and predictably changes upon deflection or the bending of the substrate.

BACKGROUND OF THE INVENTION

1. Field

This invention relates to electrical components and more particularly topotentiometers which vary in electrical resistance.

2. State of the Art

Potentiometers are standard elements of electrical and electroniccircuits. They are widely in use today for a variety of purposesincluding the measurement of mechanical movement. Even though a widevariety of potentiometers are presently available, no potentiometerknown to applicant produces a consistently and predictably variableelectrical output upon deflection or bending between variousconfigurations.

The use of electrically conductive inks in association with electricalor electronic circuitry is also known. For example, U.S. Pat. No.4,649,784 (Fulks, et al.) discloses the use of a conductive ink which ispressure sensitive to produce electrical switching signals for akeyboard. However, no flexible or deflectable potentiometer is knownwhich uses electrically conductive ink.

SUMMARY OF THE INVENTION

A flexible potentiometer comprises a substrate, conductor means andconnector means. The substrate is formed of a deflectable andelectrically insulating material. The conductor means is adhered to thesubstrate in a preselected pattern. The conductor means is formed of anelectrically conductive ink which predictably changes electricalresistance upon deflection of the substrate between a firstconfiguration and a second configuration. The connector means isassociated with the conductor means for interconnection to externalelectrical components.

The flexible potentiometer desirably includes a segmented conductoradhered to the conductor means. The segmented conductor is formed of anelectrically conductive material in segments each spaced from the otheralong the conductor means. In one embodiment, the substrate iselastically deflectable.

The electrically conductive ink is preferably of the type which isapplied to the substrate in liquid form and which in turn dries to asolid form. The segmented conductor is of the type which is applied tothe conductor means in liquid form and which also dries to a solid form.Alternatively, the segmented conductor may be a solid which is pressedonto the conductor means.

In one configuration, the substrate of the flexible potentiometer has alength with a longitudinal axis. The conductor means is a circuit havingfirst leg and a second leg each extending along the length of thesubstrate. A third leg interconnects the first leg with the second leg.The first and second legs are substantially parallel to the longitudinalaxis.

The segmented conductor preferably has a plurality of segments eachhaving a width substantially the width of the conductor means and alength selected to regulate the electrical resistance of the conductormeans. The segmented conductor is preferably made of a soft conductivemetal such as silver or a silver alloy. It may also be made of carbon ora carbon compound. Each segment is from about 2 millimeters to about 10millimeters in length.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate what is presently regarded as thepreferred embodiment for carrying out the invention:

FIG. 1 is an enlarged perspective view of a portion of a flexiblepotentiometer of the instant invention;

FIG. 2 is substantially enlarged cross-section of a portion of aflexible potentiometer of the instant invention;

FIG. 3 is a perspective of a representative potentiometer of the instantinvention;

FIG. 4 is an enlarged cross-section of a portion of a flexiblepotentiometer of the instant invention showing two other configurationsin phantom; and

FIG. 5 is a depiction of an envisioned microscopic enlargement of aportion of a flexible potentiometer of the instant invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

FIG. 1 illustrates a portion of a flexible potentiometer of the instantinvention in perspective and substantially enlarged. The flexiblepotentiometer includes a substrate 10 which is formed of a deflectableelectrical insulating material. Various types of phenolic resinmaterials are presently believed to be suitable as the substrate. Forexample, a phenolic resin Formula 3609 manufactured by ElectronicMaterials Corporation of America, 160 Commerce Drive, Montgomery, Pa.,has been found suitable in that it is elastically flexible or bendablefor many thousands of cycles or bends. At the same time it is a suitableelectrical insulator.

For applications involving multiple bending movements, the phenolicresin has been found to be particularly suitable. However, othermaterials may be suitable in selected applications. For example, thepotentiometer may be used to measure inelastic deformation so that thesubstrate itself is inelastically deformable. The critical issue is thatthe substrate be deflectable without causing an electrical discontinuityor open circuit in the conductor means while generally maintaining itselectrical insulating characteristics.

The substrate 10 illustrated in FIG. 1 has a top surface 12 to which theconductor means 14 is here applied in a preselected pattern. Forexample, in FIG. 3 the pattern is "U" shaped to present a particulardesired circuit. Other shapes may be desired to produce a variety ofdifferent electrical outputs upon deflection. At present, thepreselected pattern preferred is straight or linear as illustrated inFIGS. 1 and 3, for reasons discussed hereinafter.

The conductor means 14 of FIG. 1 is formed of an electrically conductiveink which predictably changes electrical resistance upon deflection orbending of the substrate 10 between a first configuration and a secondconfiguration. The conductor means may also be a two-part epoxymaterial, a thermoset adhesive, or a thermoplastic, all incorporatingconductive material such as graphite. The flexible potentiometer alsoincludes connector means associated with the conductor means forinterconnection to external electrical components as described withrespect to FIG. 3.

The flexible potentiometer of FIG. 1 also includes a segmented conductor16 adhered to the conductor means 14. The segmented conductor is formedof an electrically conductive material in segments 16A, 16B, 16C, 16Dand 16E, each spaced from the other along the conductor means 14.

As noted hereinbefore, FIG. 1 depicts only a portion of a flexiblepotentiometer. That is, the length 11 may be longer (or shorter) thanshown. The width 13 is greater so that the conductor means may be formedinto a complete circuit such as the one shown in FIG. 3.

Referring to FIG. 2, the substrate 10 is shown to have a thickness 18which is here shown substantially disproportionate to the true thicknessof the substrate solely to facilitate illustration. That is, for thesubstrate 10 to be elastically deflectable, it is preferred that itsthickness be from about 1/2 to about 11/2 millimeters. If it is to beinelastically deflectable, the material and thickness must beappropriately selected.

The conductor means 14 of FIG. 2 is a conductive ink which is adhered tothe substrate 10. By adhere, it is meant that the conductive ink isattached to the substrate because the conductive ink includes a materialwhich facilitates wetting, gluing, or sticking. A conductive inksuitable for the illustrated embodiment is available from VintageCapital Corporation, 140 South Chapparal Court, Suite 110, Anaheim,Calif. 92808, and is identified as Formula or Model GL 71448. Theselected ink includes graphite in combination with a binder.

As illustrated in FIG. 2, the conductive ink 14 is deposited to adhereto the substrate 10 and in turn has a thickness 20 which is hereillustrated substantially larger than the actual thickness. That is, thethickness 20 is illustrated disproportionate to the actual thickness ofthe substrate and of the actual layer of the conductive ink 14. Inparticular the thickness 20 of the conductive ink 14 is from about 0.01millimeters to 1 millimeter and desirably about 0.05 millimeters.

As illustrated in FIG. 2, a segmented conductor 16 may be positioned andadhered to the conductor means 14. The segmented conductor 16 iscomprised of a plurality of segments 16A-E as illustrated in FIG. 1. Thesegments are each spaced apart a preselected distance 22 and 24 as shownin FIG. 2. Notably, the distances 22 and 24 may be different; or theymay be selected to be substantially the same, as desired by the user.The segments are positioned on the conductive ink 14 to regulate theconductivity and in turn the electrical resistance of the conductive ink14 as more specifically discussed hereinafter.

It may also be noted that the segmented conductor is adhered to theconductive ink and in turn has a thickness 26 which is from about 0.2millimeters to about 1 millimeter and preferably about 0.5 millimeters.Each segment 16F and 16G has a length 28 selected to regulate theelectrical resistivity of potentiometer discussed hereinafter.

Referring now to FIG. 3, the substrate 10 is shown with conductor means14 positioned thereon. That is, conductor means with the segmentedconductor 16 is positioned on the substrate 10 which is deflectablebetween a first configuration illustrated with solid lines 30 and asecond configuration illustrated with dotted lines 32. Simply stated,the substrate 10 is bendable or deflectable between the configuration 30and the configuration 32. Upon deflection between the position or theconfiguration 30 and the configuration 32, the electrical resistance asmeasured between connectors 34 and 36 varies consistently andpredictably. That is, the variance in electrical resistance is not onlypredictable or known for the various deflections or configurations, butalso the variance is consistent and does not radically or randomlychange over the lifetime of the potentiometer. Thus, the substrate 10can be repetitively deflected between the configuration 30 and theconfiguration 32, and the resistance will thereby consistently andpredictably vary to reflect the deflection and the configuration.

Empirically, it has been ascertained that the deflection between thepositions 32 and 30 and all configurations therebetween can bedetermined so that the precise position of the substrate as it isdeflected between positions 32 and configuration 30 can be readilyascertained by measurement of the electrical resistance at theconnectors 34, 36 and thereafter by appropriate computations, which canbe effected using appropriate computer software as now available fromAbrams & Gentile Entertainment, Inc., 244 West 54th Street, New York,N.Y. 10019. That is, a microprocessor can be connected to the conductors34 and 36. The microprocessor has software to in turn calculate thedeflection of the flexible potentiometer between any two selectedconfigurations. That is, the microprocessor is able to compute therelative positions of certain points 37A-G along the edge 37 of thesubstrate based on the resistance detected at conductors 34 and 36 andthereafter transmit or display that information as desired. Thus, theposition or configuration of the substrate 10 and the flexiblepotentiometer is reflected by the resistance.

In FIG. 4, a portion of the flexible potentiometer is shown in a bentconfiguration A and in a further bent configuration B shown in dotedline. It is also shown in a non-deflected configuration C. Theelectrical resistance of the potentiometer consistently, predictablyvaries as the potentiometer is bent or deflected incrementally to anyconfiguration between configuration A, B and C as well as otherconfigurations involving greater bending or deflection.

As the flexible potentiometer is deflected or bent, it is believed buthas not yet been scientifically confirmed that the conductive ink whichcontains graphite, cracks or deforms as depicted in FIG. 5. That is, thedried conductive ink 14 has a granular or crystalline-type structurewhich cracks or breaks upon deflection. As the conductive ink bends, thenumber of cracks and the space between them is believed to increase,thereby changing the electrical resistance in a predictable manner. Thechange can be measured upon application of suitable electrical signals.

The segmented conductor 16 is positioned along the conductive ink 14 inpreselected lengths 28 to control or regulate the resistivity of thedeflected conductive ink 14 and in turn ensure that upon repetitivedeflections, the variation of the resistance between configurations A, Band C is consistent throughout the life of the substrate. Moreparticularly, the length and width of the segments 16 as well as thespaces 22, 24 between the segments is empirically selected to ensurethat the resistance is consistently repetitive. For example, if thewidth is the same as the width of the conductor means 14, a length 28 ofabout 3 to about 5 millimeters with spacing 22, 24 from about 1 to about2 millimeters has been found suitable for a flexible potentiometersimilar to that of FIG. 3 with a length 44 of about 10 centimeters and awidth of about two centimeters.

The segmented conductor 16 has been successfully formed of silver. It isalso believed formable from conductive silver alloys, and otherconductive metals, as well as carbon-based compounds. The segmentedconductor 16 retains its electrical conductivity upon deflection.

With the segmented conductor 16 affixed or adhered to the conductormeans 14, the resistance may still vary somewhat over time, but thedegree of variance is either within acceptable tolerances or otherwisemeasurable from time to time so that adjustments can be made toaccommodate for the drift in resistance over time.

Referring to FIG. 3, it can be seen that the flexible potentiometer hereillustrated has a first leg 38 and a second leg 40 both of which aresubstantially parallel to an axis 42 of the substrate 10 which has anoverall length 44 as well as a width 46. The first leg 38 and the secondleg 40 extend lengthwise and are interconnected by a third leg 48 toform the desired configuration of the conductor means 14. Notably, onlyone leg 38 has a conductor means 14 with a segmented conductor 16 asshown in FIGS. 1, 2 and 4. The other leg 40 has a conductor which doesnot vary in resistance upon deflection. In the embodiment illustrated,the leg 40 has conductor means 14 with the segmented conductor thereon,without segments so that it is continuous and unbroken.

It may be noted that the connectors 34 and 36 are slide connectors whichare riveted onto the substrate 10 or otherwise affixed thereto toelectrically interconnect the first leg 38 and the second leg 40 withexterior electrical components such as a microprocessor hereinbeforediscussed but not here illustrated.

In use, the substrate 10 is deflected repetitively and the deflectionthereof may be measured by measuring the variance in resistance at theconnectors 34 and 36. Thus, the resistance and in turn the movement ordeflection of a variety of objects can be measured accurately. Forexample, the substrate 10 can be configured to be attached to a fingerof a human being. By bending the finger, the resistance of theconductive ink and in turn the entire flexible potentiometer varies asmeasured at the output of the flexible potentiometer and moreparticularly the connectors 34 and 36 so that the movement of the fingercan be calculated as hereinbefore discussed.

It should be appreciated that reference herein to the details of theillustrated embodiment is not intended to limit the scope of the claims,which themselves recite those features regarded as essential to theinvention.

What is claimed:
 1. A flexible potentiometer comprising:a substrateformed of a deflectable electrical insulating material, said substratehaving a length, an upper surface and a lower surface which is spacedfrom and in general alignment with said upper surface; conductor meansto conduct electricity as part of an electrical circuit and adhered toone of said upper surface and said lower surface of said substrate in apreselected pattern extending along the said length of said substrate,said conductor means being formed of an electrically conductive inkwhich changes electrical resistance upon movement of said conductormeans and said upper surface and said lower surface all togethergenerally transversely to the length of said substrate between a firstconfiguration and a second configuration; and connector means associatedwith said conductor means for interconnection to external electricalcomponents.
 2. A flexible potentiometer comprising:a substrate formed ofa deflectable electrical insulating material having an upper surface anda lower surface spaced from and in general alignment with said uppersurface; conductor means adhered to one of said upper surface and saidlower surface of said substrate in a preselected pattern, said conductormeans being formed of an electrically conductive ink which changeselectrical resistance upon deflection of said conductor means and saidupper surface and said lower surface all together between a firstconfiguration and a second configuration; connector means associatedwith said conductor means for interconnection to external electricalcomponents; and segmented conductor adhered to said conductor means,said segmented conductor being formed of an electrically conductivematerial in segments each spaced from the other.
 3. The flexiblepotentiometer of claim 1 wherein the substrate is elasticallydeflectable.
 4. The flexible potentiometer of claim 1 wherein saidelectrically conductive ink is of the type which is applied to saidsubstrate in liquid form.
 5. A flexible potentiometer comprising:asubstrate formed of a deflectable electrical insulating material havingan upper surface and a lower surface spaced from and in generalalignment with said upper surface; conductor means adhered to one ofsaid upper surface and said lower surface of said substrate in apreselected pattern, said conductor means being formed of anelectrically conductive ink which changes electrical resistance upondeflection of said conductor means and said upper surface and said lowersurface between a first configuration and a second configuration; asegmented conductor adhered to said conductor means, said segmentedconductor being formed of an electrically conductive material insegments each spaced from the other, said segmented conductor being ofthe type that is applied to said conductor means in liquid form anddries to a solid form.
 6. The flexible potentiometer of claim 2 whereinsaid segmented conductor is a solid material to be pressed onto saidconductor means.
 7. The flexible potentiometer of claim 2 wherein saidsubstrate has a length with a longitudinal axis and is deflectablebetween said first configuration and said second configuration alongsaid longitudinal axis.
 8. The flexible potentiometer of claim 7 whereinsaid preselected pattern of said conductor means is a circuit having afirst leg extending along said length, a second leg extending along saidlength and a third leg interconnecting said first leg with said secondleg.
 9. The flexible potentiometer of claim 8 wherein said first leg andsaid second leg are substantially parallel to said longitudinal axis.10. The flexible potentiometer of claim 8 wherein said conductor meanshas a width, wherein said segmented conductor has a plurality ofsegments each having a width substantially the width of said conductormeans and a length selected to regulate the electrical resistance ofsaid conductor means.
 11. The flexible potentiometer of claim 10 whereinsaid segmented conductor is made of a soft conductive metal.
 12. Theflexible potentiometer of claim 11 wherein the segmented conductor ismade of silver or a silver alloy.
 13. The flexible potentiometer ofclaim 10 wherein the segmented conductor is made of carbon or a carboncompound.
 14. The flexible potentiometer of claim -0 wherein eachsegment is from about two millimeters to about ten millimeters inlength.
 15. For measuring or detecting deflection, a flexiblepotentiometer comprising:a substrate having a length and a width, saidsubstrate being formed of an elastically deflectable and electricallyinsulating material; an electrically conductive ink adhered to saidsubstrate in a pattern having a first leg and a second leg eachextending lengthwise of said substrate and elastically deformable topredictably change electrical resistance upon deflection of saidsubstrate from a first configuration to a second configuration; asegmented conductor adhered to said electrically conductive ink, saidsegmented conductor being formed of an electrically conductive materialdeposited on said electrically conductive ink in spaced apart segments;and connector means associated with said electrically conductive ink forinterconnection to external electrical components.
 16. A flexiblepotentiometer comprising:a substrate formed of an electrical insulatingmaterial, said substrate having an upper surface and a lower surface,spaced from and in general alignment with said upper surface, saidsubstrate having a longitudinal axis and said substrate being bendablegenerally transversely to said longitudinal axis between a firstconfiguration and a second configuration in which said upper surface andsaid lower surface are together bent transverse to said longitudinalaxis; conductor means adhered to one of said upper surface and saidlower surface of said substrate in a preselected pattern to be bendableupon bending of said substrate, said conductor means being formed of anelectrically conductive ink which changes electrical resistance uponsaid bending of said conductor means and said substrate between saidfirst configuration and said second configuration; and connector meansassociated with said conductor means for interconnection to externalelectrical components.
 17. A method for varying the resistance inanelectrical circuit comprising: providing a substrate formed of adeflectable electrical insulating material, said substrate having alength, an upper surface and a lower surface which is spaced from and ingeneral alignment with said upper surface; providing conductor means forconducting electricity as part of an electrical circuit and adheringsaid conductor means to one of said upper surface and said lower surfaceof said substrate in a preselected pattern extending along the saidlength of said substrate, said conductor means being formed of anelectrically conductive ink which changes electrical resistance uponmovement of said conductor means and said upper surface and said lowersurface all together generally transversely to said length between afirst configuration and a second configuration; providing connectormeans for connection to external electrical components; connecting saidconnector means to said conductor means and to external electricalcomponents in said electrical circuit; and bending said substrate andsaid conductor means between a first position and a second position.